The effect of heat shock on M-cholinoreceptors from rat cerebral cortex membranes

The major parameters of binding the specific blocker [3H]quinuclidinyl benzylate were obtained for M-cholinoreceptors of rat cerebral cortex membranes. One receptor was shown to bind two molecules of the ligand; two discrete receptor pools were revealed, which differed in the sensitivity (Kd1 = 0.35 +/- 0.03; Kd2 = 1.79 +/- 0.21 nM) and the number of the ligand binding sites (B1 = 468 +/- 54; B2 = 864 +/- 81 fmol/mg protein). Heat shock decreased the number of receptors of the high-affinity pool (B1) by 16% (Kd1 did not differ from the control); the efficiency of the ligand binding to the receptors (E = B/2Kd) decreased by 26%, which suggests the decrease in the functional activity of the receptors of this pool. In the low-affinity pool (B2), the number of receptors increased by 39%, and Kd2 decreased by 22%; the efficiency (E2) increased by 14%.